1. Field of the Invention
The present invention relates to mainly a blood pump apparatus for transporting a physiological fluid such as blood and, more particularly, to a blood pump apparatus capable of suppressing turbulence of a blood component to be transported and enhancing good pump characteristics at a low speed.
2. Description of the Related Art
Known turbo pump apparatuses for transporting a physiological fluid such as blood or plasma are described in U.S. Pat. Nos. 4,589,822 and 3,864,055. These pumps are turbo pumps for feeding blood using centrifugal forces. The former turbo pump generates the centrifugal force upon rotation of a general open type multi-blade vane assembly, while the latter turbo pump generates the centrifugal force by utilizing a friction force between a plurality of conical rotators.
The most important things for blood transportation are to prevent solid components such as erythrocytes and platelets in the blood from being destroyed and to prevent the blood from coagulating as a result of contact with foreign materials. The most important cause for destruction of the above Solid components is blood turbulence during transpiration. The blood pump disclosed in U.S. Pat. No. 3,864,055 is a pump for applying the centrifugal force to the fluid by the friction force between the plurality of conical rotators. This pump is known as a pump for minimizing turbulence in a blood path between the rotators and hence destruction of solid components (Hydrodynamical and Hemodynamical Evaluation of Rotary Blood Pumps: Inter. Workshop on Rotary Blood Pumps: Vienna. 1988 pp. 76-81).
This blood pump, however, has pump efficiency lower than that of a general pump using vanes. In order to obtain a given pump head, the above blood pump requires a higher speed than that of a vane pump having the same size. For this reason, local heating occurs in a seal portion of a rotating shaft, and the blood around the rotating shaft is denatured and coagulated. In order to obtain the same flow rate as the vane pump having the same size, the blood pump requires a plurality of rotators. Since these plural rotators are housed in the pump housing, the volume of the housing is increased, leading to an increased priming volume, i.e., the amount of blood loaded in the pump housing.
On the other hand, the blood pump described in U.S. Pat. No. 4,589,822 uses an open type multi-blade vane assembly having a large opening at its center to reduce local heating at the seal portion of the shaft, so that the blood speed near the seal portion is increased. In addition, a heat sink structure is added to this pump. In the open type vane pump of this type, however, the blood flow tends to be separated from the vanes, vortex and a counter flow tends to occur between the vanes. So, the blood flow tend to be turbulent, and solid components (e.g., erythrocytes) in the blood tend to be destroyed.
In the conventional pump of this type, erythrocytes are likely to be destroyed (so called hemolysis). Also, the function of the blood platelet tends to be lowered. It follows that the conventional pump of this type is not adapted for use over a long period of time. Incidentally, a high pump head can be obtained in general with a low rotation speed in the case of enlarging the pump housing. However, the enlargement of the pump housing gives rise to an inconvenience that the priming volume of the pump is increased.